// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
#define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "content/common/content_export.h"
#include "content/public/browser/readback_types.h"

class SkBitmap;

namespace content {

class NavigationControllerImpl;
class NavigationEntryImpl;
class RenderViewHost;
class ScreenshotData;

// NavigationEntryScreenshotManager takes care of taking image-captures for the
// current navigation entry of a NavigationControllerImpl, and managing these
// captured images. These image-captures are used for history navigation using
// overscroll gestures.
class CONTENT_EXPORT NavigationEntryScreenshotManager {
public:
    explicit NavigationEntryScreenshotManager(
        NavigationControllerImpl* controller);
    virtual ~NavigationEntryScreenshotManager();

    // Takes a screenshot of the last-committed entry of the controller.
    void TakeScreenshot();

    // Clears screenshots of all navigation entries.
    void ClearAllScreenshots();

protected:
    virtual void TakeScreenshotImpl(RenderViewHost* host,
        NavigationEntryImpl* entry);

    // Called after a screenshot has been set on an NavigationEntryImpl.
    // Overridden in tests to get notified of when a screenshot is set.
    virtual void OnScreenshotSet(NavigationEntryImpl* entry);

    NavigationControllerImpl* owner() { return owner_; }

    void SetMinScreenshotIntervalMS(int interval_ms);

    // The callback invoked when taking the screenshot of the page is complete.
    // This sets the screenshot on the navigation entry.
    void OnScreenshotTaken(int unique_id,
        const SkBitmap& bitmap,
        ReadbackResponse response);

    // Returns the number of entries with screenshots.
    int GetScreenshotCount() const;

private:
    // This is called when the screenshot data has beene encoded to PNG in a
    // worker thread.
    void OnScreenshotEncodeComplete(int unique_id,
        scoped_refptr<ScreenshotData> data);

    // Removes the screenshot for the entry, returning true if the entry had a
    // screenshot.
    bool ClearScreenshot(NavigationEntryImpl* entry);

    // The screenshots in the NavigationEntryImpls can accumulate and consume a
    // large amount of memory. This function makes sure that the memory
    // consumption is within a certain limit.
    void PurgeScreenshotsIfNecessary();

    // The navigation controller that owns this screenshot-manager.
    NavigationControllerImpl* owner_;

    base::Time last_screenshot_time_;
    int min_screenshot_interval_ms_;

    // Taking a screenshot and encoding them can be async. So use a weakptr for
    // the callback to make sure that the screenshot/encoding completion callback
    // does not trigger on a destroyed NavigationEntryScreenshotManager.
    base::WeakPtrFactory<NavigationEntryScreenshotManager> screenshot_factory_;

    DISALLOW_COPY_AND_ASSIGN(NavigationEntryScreenshotManager);
};

} // namespace content

#endif // CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
